1. Field of the Invention
The present invention relates to a current sensor for detecting a currentless state and a method for detecting a currentless state with a current sensor.
2. Description of the Background Art
JP 57118661 A discloses a current sensor. Non-contact measurement of a current flowing in a conductor can be carried out with a current sensor of this type. In the simplest embodiment, a magnetic field generated by the current flow in a conductor can be measured with a Hall sensor alone. To reduce scattering effects and other interference effects, however, a ring is typically used which is made of a magnetic conductive material and has a slot in which a Hall sensor is disposed. If such a ring-shaped current sensor surrounds a conductor, the magnetic field generated by the conductor can be focused and the current flow in the conductor can be determined more precisely. However, the association between the magnetic field strength and the flux density in magnetically conductive material is not linear and the use of the current sensor is limited to a predetermined current range.
EP 0 742 440 B1 discloses a current sensor which is constructed according to the principle of a compensation current transformer. According to the compensation principle, the ring made of a magnetically conductive material is equipped with a winding through which a current is sent, which is intended to work against the current in the conductor with respect to the particularly generated magnetic field. In this case, this type of compensation current sensor is typically regulated so that the magnetic field present at the Hall sensor is regulated to zero. Therefore, the current flowing through the winding is directly proportional to the current to be measured and flowing in the conductor. At present, in this case, the Hall sensor is supplied with a constant operating current, so that with respect to its magnetic field sensitivity it is adjusted to a fixed sensitivity range.
In addition, DE 10 2004 010 613 A, which corresponds to U.S. Pat. No. 7,825,657, discloses a regulating system for a magnetic field sensor, in which the signals are processed digitally by means of a processor. Further, DE 10 2006 017 479 A1 (which corresponds to U.S. 20090189575) and DE 42 19 025 A1 (which corresponds to U.S. Pat. No. 5,315,293) disclose a method for measuring an alternating current or a method for detecting an overcurrent, respectively.